Safety adapter for three-wire grounding plug

ABSTRACT

The present invention relates to safety adapter for electrically connecting a three-wire grounding plug to a two-pole two-wire outlet and automatically establishing a ground connection through the outlet when installed in a service box in a grounded system. It relates, more particularly, to safety features of the adapter. The adapter includes a body of insulating material having a pair of spaced blades extending outwardly from one face thereof and fitting into female contacts of the two-wire outlet. The adapter body carries a pair of flexible guard fingers which extend downwardly on opposite sides of the blades into engagement with a face of the outlet as the blades are being inserted. The fingers prevent a metal cover or wall plate from coming into contact with the blades as the adapter is being installed and a ground connection to the adapter is being made. They also prevent the fingers of a person from coming into contact with the blades.

United States Patent Lopez [111 3,865,453 1 Feb. 11, 1975 [75] Inventor: Juan M. Lopez, New York, N.Y.

[73] Assignee: Leviton Manufacturing Co., Inc.,

Little Neck, N.Y.

[22] Filed: Oct. 5, 1973 [21] Appl. No.: 403,914

[52] US. Cl. 339/14 R, 339/40, 339/156 R [51] Int. Cl. H0lr 3/06, HOlr 13/50 [58] Field of Search 339/14, 36, 40, 42, 153-156, 339/184 R [56] References Cited UNITED STATES PATENTS 2,458,153 l/1949 Festge 339/42 UX 3,763,457 10 1973 Whippo 339/42 Primary ExaminerJames T. McCall Assistant Examiner-Lawrence J. Staab Attorney, Agent, or Firm-Hanse H. Hamilton [57] ABSTRACT The present invention relates to safety adapter for electrically connecting a three-wire grounding plug to a two-pole two-wire outlet and automatically establishing a ground connection through the outlet when installed in a service box in a grounded system. It relates, more particularly, to safety features of the adapter. The adapter includes a body of insulating material having a pair of spaced blades extending outwardly from one face thereof and fitting into female contacts of the two-wire outlet. The adapter body carries a pair of flexible guard fingers which extend downwardly on opposite sides of the blades into engagement with a face of the outlet as the blades are being inserted. The fingers prevent a metal cover or wall plate from coming into contact with the blades as the adapter is being installed and a ground connection to the adapter is being made. They also prevent the fingers of a person from coming into contact with the blades.

4 Claims, 8 Drawing Figures PATENTEDFEBI 1 i- 3,865.453

' SHEEI 2 OF 2 SAFETY ADAPTER FOR THREE-WIRE GROUNDING PLUG The present invention relates to a safety adapter for a three-wire grounding plug.

It relates, more particularly, to an adapter for connecting a two-pole two-wire outlet to a three-wire grounding plug. The adapter contains a female U- shaped ground contact and a pair of spaced female contacts which accept mating contacts of a three-wire grounding plug and automatically establishes a ground connection to the plug.

Generally speaking, such adapters are. well known and are employed to connect a three-wire grounding plug to a two-wire outlet having two female contacts which are connected to a power line. The adapter has three female contacts which will accept the male blades of a three-wire grounding plug and automatically establishes a ground connection to one of the blades of the plug.

An object of the invention is to preclude the possibility of a short circuit when the adapter is being installed or removed. To establish the ground connection, a mounting screw of a metal. cover or wall plate is removed and a grounding strap of the adapter is connected to a grounded part of an outlet by means of the screw. Ordinarily, the mounting screw engages with a mounting strap or yoke of the two-wire outlet having ends which rest on and are grounded through an outlet box in a grounded system. When the male blades of the adapter are inserted in the female contacts of the outlet, they automatically positionan opening in one of two grounding straps of the adapter in register with an opening in the cover plate for the screw. While the mounting screw is removed, the metal cover. plate is loose and may accidentally be moved'into contact with the male blades of the adapter. If this happens, a short circuit will result.

To prevent this, the subject adapter incorporates a pair of flexible guard fingers which extend downwardly along opposite sides of the blades-of the adapter into engagement with the face of theoutlet and with the metal cover plate as the adapter is beinginstalled or removed. Thus, the guard fingers prevent the cover plate or the fingers of a person from coming into contact with the blades of the adapter when the blades are partially inserted and .are live electrically.

Other objects and advantages of the invention will become apparent and be more clearly understood from the following description and the accompanying drawings in which:

FIG. 1 is a side view of an adapter embodying the invention;

FIG. 2 is a side view of the adapter shown in FIG. 1 as seen from the right;

FIG. 3 is a bottom plan view of the adapter shown in FIG. 2 with the grounding straps broken away;

FIG. 4 is a top plan view of the adapter shown in FIG.

FIG. 5 is an end view in partialv section showing the adapter shown in FIG. 2 installed in a single two-wire outlet of a duplex receptacle and with the guard fingers of the adapter collapsed by engagement with a cover plate surrounding the receptacle;

FIG. 6 is a section view taken along line 6-6 of FIG.

FIG. 7 is a fragmentary view in horizontal section illustrating possible movement of the cover plate surrounding the receptacle;

FIG. 8 is a view in perspective showing a modified form of an adapter embodying the invention.

Referring now to the drawings in detail, there is an adapter 10 having a body II formed of an insulating material such as a vinyl compound.

As noted, the adapter body is of conventional shape and hence, requires only a brief description. Briefly, the adapter body 11 contains a pair of spaced female contacts 12 and 13 which communicate with spaced openings 14 and 15 in an upper face of the body II to receive and make contact with a pair of spaced male blades of a three-wire grounding plug (not shown).

The female contacts 12 and 13 are connected to male contact blades 16 and 17, which extend downwardly from a lower face of the body and are spaced to fit into openings 18 and 19 containing female contacts (not shown) of a two-wire outlet 20. As will be understood, the contacts of the outlet 20 are normally connected to a source of power.

As illustrated, the outlet 20 is one outlet of a pair of outlets forming a standard'two-pole two-wire duplex receptacle. However, it will be understood that the subject adapter may be employed with other types of twowire outlets which do not have grounding contacts.

It is also noted that the male contact blades 16 and 17 are of different widths and are polarized in this manner. Due to this, the adapter 10 can only be installed in one position in the outlet 20.

In addition to the contacts 12 and 13, a third or ground contact 21 is also contained in the body 11. The ground contact 21 has a female upper end 22 of a standard U-shaped configuration which communicates with a third opening 23 in the upper face of the adapter to receive and mate with a ground blade carried by the three-wire grounding plug.

To complete the ground connections, grounding straps 24 and 25 are attached to the ground contact 21 and extend outwardly from opposite sides of the body 11 adjacent the lower face thereof. The ground straps 24 and 25 are formed from bendable strips of conductive material and contain slotted opening 26 and27 at their outer ends. When the blades 16 and 17 of the adapterare fully inserted in the female contacts of the outlet 20, as indicated in FIG. 6, the slotted opening 26 or 27 in one of the ground straps 24 or 25 will register with a central opening 28 in a cover or wall plate 29 which receives a mounting screw 28a. As shown, the ends of the ground straps 24 and 25 are of different lengths to permit the adapter 11 to be plugged into either outlet of the duplex receptacle as desired and the particular openong 26 or 27 employed for extablishing the ground connection will depend on which outlet is used. Due to the polarization, the adapter cannot merely be reversed.

The mounting screw 28a engages with a mounting strap or yoke (not shown) for the receptacle having ends which rest on an outlet box (not shown) and is grounded thereby in a grounded system. Thus, the screw 28a establishes a ground connection between the yoke and the ground straps 24 or 25.

To establish the desired ground connection to one of the straps 24 or 25 of the adapter, the mounting screw 28a is ordinarily removed from the cover plate and is then replaced after the adapter has been inserted in the outlet with the male blades 16 and 17 in engagement with the female contacts of the outlet. During this operation, the cover plate 29, which may be made of metal is free to move and may accidentally come into contact with the male blades 16 and 17 of the adapter, causing a short circuit.

To avoid this possibility, the adapter is provided with guard means which engage with and prevent the metal cover plate from coming into contact with the male blades of the adapter during insertion of the adapter. The guard means, illustrated in FIG. 1, comprises a pair of flexible fingers 30 and 31 which are carried by the body 10 and extend downwardly therefrom on opposite sides of the male blades 16 and 17. As shown, the guard gingers 30 and 31 are wider than the blades 16 and 17 and are long enough to engage with the face of the outlet or receptacle before the ends of the male blades are in electrical contact with the female contacts of the outlet. The guard fingers also protect the fingers of a person from contacting the blades while serving as convenient finger grips.

As illustrated in FIG. 7, the guard fingers will be interposed between edges of an opening in the cover plate 29 and the male blades 16 and 17 of the adapter as the blades are being introduced into the outlet. This takes place before the blades come into contact with the female contacts of the outlet and prevents the cover plate 29 from coming into contact with the male blades 16 and 17 of the adapter at this time.

To increase their flexibility, the guard fingers 30 and 31 are corrugated as indicated at 30a and 31a and are joined to the lower end of the adapter body 11 by grooves 32 and 33 which permit the guard fingers to bend outwardly. When the adapter 10 has been fully inserted in the outlet, as shown in FIG. 5, the guard fingers 30 and 31 press against the cover plate and hold the cover plate against movement while the mounting screw 28a is being replaced.

In the embodiment of the invention, shown in FIG. 8, the guard means is in the form of collapsible bands 34 and 35 which extend beyond the contact blades 16 and 17 of the adapter 10 and collapse into' recesses at the sides thereof when the adapter is installed. Otherwise, corresponding parts are identified by the same reference numerals.

Ends of the collapsible bands 34 and 35 are connected to the body of the adapter above the blades 16 and 17 and thus, can assume a flattened condition when the adapter has fully been inserted in the outlet without interference with the insertion of the male blades.

In this condition, it is also noted that the guard means may be formed integrally with the adapter body or may be formed as separate pieces which can be attached thereto.

While preferred embodiments of the invention have been described and illustrated herein, various modifications and changes may be made therein by persons skilled in the art without departing from the spirit or scope of the invention.

What is claimed is:

1. In an adapter for converting a two-wire parallel outlet to a three-wire ground outlet, said adapter having a body of insulating material with two parallel contact blades extending from a lower face thereof and spaced female contacts including a grounding contact on an upper face thereof, the improvement which comprises:

a. a pair of ground straps connected to a ground contact in an adapter body;

b. said ground straps having outer ends extending beyond the adapter body adjacent a lower face thereof and on opposite sides thereof;

c. each of said ground straps having an outer end containing an opening for receiving a grounding screw; and

d. collapsible guard means extending downwardly from the adapter body on opposite sides of parallel male blades of the adapter and positioned for engagement with an opposing face of a receptacle prior to engagement of said male blades with female contacts of a receptacle;

e. said guard means comprising members collapsible to a flattened condition upon entry of the male blades into said female contacts.

2. In an adapter as defined in claim 1, wherein:

a. the guard means comprises a pair of flexible fingers extending downwardly from the adapter body on opposite sides of the parallel male blades.

3. In an adapter as defined in claim 2, wherein:

a. said fingers are formed integrally with the adapter body and have serrated outer surfaces imparting flexibility to the fingers.

4. An adapter for establishing electrical connections between a three-wire plug and a two-wire outlet, which comprises:

a. a body formed of insulating material;

b. said body containing spaced female contacts which include a ground contact and a pair of spaced parallel contact blades extending downwardly from a lower face thereof;

c. said blades being connected respectively to two of the female contacts in the body;

d. a pair of metal ground straps connected to said ground contact in the body and having ends extending outwardly from opposite sides of the body adjacent said lower face thereof;

e. each of said straps having an exposed outer end containing an opening for receiving a ground screw;

f. said openings in said straps being located at different distances from the sides of the body; and

g. a pair of collapsible guard fingers carried by the body and extending downwardly therefrom on opposite sides of the male contact blades;

. said guard fingers having lower ends engaging with a face of an opposing outlet prior to engagement of the male contact blades with female contacts of the outlet;

i. said fingers being interposed between a wall plate and the male blades of the adapter when a ground connection is made to either of said ground straps. 

1. In an adapter for converting a two-wire parallel outlet to a three-wire ground outlet, said adapter having a body of insulating material with two parallel contact blades extending from a lower face thereof and spaced female contacts including a grounding contact on an upper face thereof, the improvement which comprises: a. a pair of ground straps connected to a ground contact in an adapter body; b. said ground straps having outer ends extending beyond the adapter body adjacent a lower face thereof and on opposite sides thereof; c. each of said ground straps having an outer end containing an opening for receiving a grounding screw; and d. collapsible guard means extending downwardly from the adapter body on opposIte sides of parallel male blades of the adapter and positioned for engagement with an opposing face of a receptacle prior to engagement of said male blades with female contacts of a receptacle; e. said guard means comprising members collapsible to a flattened condition upon entry of the male blades into said female contacts.
 2. In an adapter as defined in claim 1, wherein: a. the guard means comprises a pair of flexible fingers extending downwardly from the adapter body on opposite sides of the parallel male blades.
 3. In an adapter as defined in claim 2, wherein: a. said fingers are formed integrally with the adapter body and have serrated outer surfaces imparting flexibility to the fingers.
 4. An adapter for establishing electrical connections between a three-wire plug and a two-wire outlet, which comprises: a. a body formed of insulating material; b. said body containing spaced female contacts which include a ground contact and a pair of spaced parallel contact blades extending downwardly from a lower face thereof; c. said blades being connected respectively to two of the female contacts in the body; d. a pair of metal ground straps connected to said ground contact in the body and having ends extending outwardly from opposite sides of the body adjacent said lower face thereof; e. each of said straps having an exposed outer end containing an opening for receiving a ground screw; f. said openings in said straps being located at different distances from the sides of the body; and g. a pair of collapsible guard fingers carried by the body and extending downwardly therefrom on opposite sides of the male contact blades; h. said guard fingers having lower ends engaging with a face of an opposing outlet prior to engagement of the male contact blades with female contacts of the outlet; i. said fingers being interposed between a wall plate and the male blades of the adapter when a ground connection is made to either of said ground straps. 